The present invention relates to an AGC (automatic gain control) circuit for suppressing fluctuation of an input signal by controlling the gain of a variable gain amplifier circuit, in a communication system or a speech system, according to the amplitude of the input signal so that the amplitude of an output signal becomes constant.
An AGC circuit controls the amplitude of an input signal which fluctuates due to a variety of causes to a constant amplitude by an amplifier for controlling a gain and outputs the controlled signal. For example, an AGC circuit having a configuration using an integrator circuit with a capacitor is disclosed in Japanese Laid-Open Publication No. 8-116226.